Process of making pressure sensitive record material



PROGESS OF MAKING PRESSURE SENSITIVE RECORD MATERIAL Barrett K. Green, Dayton, Ohio, assignor to The National Cash Register Company, Dayton,

Ohio, a corporation of Maryland No Drawing.

Original application November 8,

1947, Serial No. 784,939. Divided and this application December 2, 1948, Serial No. 63,215

2 Claims. "it

This invention relates to improvements in process of making a pressuresensitive record material. This application is a division of the pending application of Barrett K. Green, Serial No. 784,939, filed November 8, 1947, for Process of making pressure-sensitive record material.

The principal object of this invention is to provide a process of making a pressure-sensitive record material, on which a mark of distinctive color may be produced by the mere application of localized pressure, and which is not subject to the disadvantages inherent in the pressure-sensitive record material disclosed in United States Letters Patent No. 2,299,693, patented October 20, 1942, on the application filed by Barrett K. Green on February 23, 1940. That patent discloses a pressure-sensitive record material including the combination of an insulating medium, rupturable solid material such as gum dammar, having included therein interspersed droplets of a plurality of liquid reagents, which are chemically reactive to produce a distinctive color in the record material at the points of application of localized pressure thereto, such pressure rupturing the insulating medium to permit chemical reaction between the two liquid reagents. The two reagents disclosed in this patent are gallic acid and ferric ammonium sulphate, each dissolved in glycerine. These reagents are ionized by the glycerine, which constitutes an ionizing medium, and the chemical reaction proceeds by interchange of ions when the two solutions are allowed to mix, upon the rupture of the insulating medium. The reaction disclosed in that patent depends upon the presence of the reagents in an ionizing medium. However, any available ionizing medium is hygroscopic, with the result that the record material, made in accordance with this patent, is sensitive to an excess of moisture, and conditions of high humidity may cause the insulating medium to cease to be efiective, with the result that the chemical reaction takes place without any application of localized pressure, and the record material is stained and discolored, so that it ceases to be useful.

As stated above, the principal object of the present invention is to provide a process of making a pressure-sensitive record material that is not subject to the defects and disadvantages of that disclosed in Patent No. 2,299,693, as indicated above.

Another object of the present invention is to provide a process of making a record material upon which a mark of distinctive color may be produced, at points of application of localized pressure, thereto, by such mere application of localized pressure, and which will not become discolored or stained due to the effect of light, atmospheric conditions, or aging.

In short, it is the object of this invention to provide a process of making a pressure-sensitive record material in which the mark of distinctive color will be produced only at the points of application of localized pressure, and at no other points, and under no other conditions.

Another object of this invention is to provide a process of making a pressure-sensitive record material in which the mark of distinctive color is produced by the chemical reaction of color-forming reactants, in the absence of any liquid ionizing medium therefor.

A further object of this invention is to provide a process of making a pressure-sensitive record material in which a mark of distinctive color is produced by a reaction between solid particles of color-forming reactants.

Further objects, and objects relating to details and economies of operation, will definitely appear from the detailed description to follow. The objects of this invention have been attained by the several embodiments thereof described in detail in the following specification. This invention is clearly defined and pointed out in the appended claims.

In general, the present invention contemplates a process of making a pressure-sensitive record material including the forming on a supporting member a film-like deposit of solid particles of a plurality of adsorption color-forming reactants disposed in contiguity with each other, such reactants being so selected that they react, in the absence of a liquid ionizing medium for the reactants, to form a distinctive color when brought into contact with each other, and a solid insulating medium insulating said reactants from coloriorming reaction contact with each other. Upon application of localized pressure to the record material, as by drawing a stylus across it, the insulating medium is ruptured at the points of application of said localized pressure, and such rupture permits color-forming reaction contact between the reactants at such points, in the absence of any liquid ionizing medium for said reactants. The result i that a mark of distinctive 3 color is produced by the mere application of localized pressure.

The color reaction employed is of the, so-called, adsorption type wherein an inorganic compound causes a color change in an organic compound coming into adsorption contact therewith.

Of the reactant materials employed the organic material is. an electron donor. aromatic compound havinga double bond system which is convertible to a more highly polarized conjugated form upon taking part in an electron acceptordonor solid surface chemical reaction, giving it a distinctive color, and the inorganic material is a material which is an acid relative to the organic material so as to be an electron acceptor when in adsorption contact therewith. Bothmaterials are in fine particle form in order to furnish a large reactant surface area per unit area of the record material which enhances thedepth of 00101 per unit area of the record material.

According to one embodiment of the invention, solid particles of one of the color-forming re.- actants are carried by and dispersed in a solid iiusu ati svmsd u nto which a c a o solid :,par cles. f.anotheiqcolor-formingreactant is applie g lin this case, the application of localized :.p es.s 161 3 9 26 h so n u a i g me m at -IQIB5PO11I1S of application of such pressure, and .brgings aboutcol or-forming reaction contact between the solid particles of color-forming re- .actants a csuch po s. th p d et a -;.Qf distinctive color. Preferably, this pressurez-lsensitive record material includes a base web, -such..a.s .a fibrous web of paper or the like, to ".whichsthecoatingof solid insulating mediumand the color-formingreactantsis applied.

The insulating medium is a pressure-rupturaable :zfilm derived from an organic film-forming 'hydrophilic colloid substance.

.;Sinc.e..-it;is.difficultgto show precisely the spatial ii,

The casein constitutes the solid insulating medium, which insulates the solid particles of kaolin from color-forming reaction contact with the solid particles of 3,3 bis(p-diethylaminophenyl) fphtha'lide. The material is normally white, but application of localized pressure thereto, as by drawing a stylusacross it, produces ablue-green mark at the' points of application of such pressure, due to the localized rupture of the insupaperhaving been dried, its coatedside was next treated with a 3% by weight solution in toluene of the compound 3,3 bis(p-diethylaminophenyl) phthalide. The excess of solution was then removed, andithe treated paper was dried to evaporatethe solvent.

Another embodiment of this invention produces apressure-sensitlve record material comprising a webof paper having applied thereto a coating including casein asthe s01id insulating medium and solid particles .of two color-forming reactants;

namely, kaolin and the compound 3,3 bis(p-di-npropyl aminophenyl) phthalide, having the struc- .turaL-formula This .recordmaterial is normallywhitebut the applicationof localized pressure thereto ruptures the insulating medium; casein, at :the pointsof application of such pressure,permitting colorforming reaction contact between thesolid particles of kaolin and the solid particles .of the compound 3,3 .bis(p-dien-propylaminophenyl) phthalide, resultin in the productionof a blue- .green mark.

The record material .just described has been successfully made, in accordance .with thisembodiment of the invention, by coating a .webof paper with a casein solution having solid particles of kaolin dispersedtherein, the ratioof kaolin to casein being about ten to one. .The paper so coated was dried and the coated .side of the paper treated with a.3% solution in toluene of the compound 33 bis(psdi-n-propylaminophenyl) phthalide. The excess of.-so1ution was removed,

.and thetreated paper was dried to evaporatethe solvent.

When the ingredients in eitherembodimentare applied .to the paper .as a coating thereon, such coating should weigh about .0023 pound per squarefoot of surface .and should have .a thicknessof the order of from .0005 110.001 inch. The thickness of the coating varies, of course, with the treatment to which .the record material :is subjected in finishing. The solid particles of kaolin in this record material may be of about the order of ten microns .in diameter, although considerable variation in particle size is possible without any ill .eifects. Particle size of the phthalidematerial is largelydetermined by the method of application .of that ingredient. .The particles of these reactants may be as large as ten microns in diameter and frequentlyare much smaller.

Otherorganic film-forming hydrophilic colloid substances .such as gelatin, methyl cellulose, starch, polyvinyl alcohol, .and animal :glue are representative materials that may be substituted for-casein as thesolid insulating medium. Any

of the following inorganic materials may be substituted for kaolin as one of the color-forming reactants: attapulgite (Attapulgus clay), pyrophyllite, talc, bentonite, halloysite, calcium sulphate, calcium citrate, magnesium trisilicate, zinc sulphide, zirconium dioxide, calcium phosphate, barium sulphate, and calcium fluoride. When any of these materials are substituted for the kaolin in this combination, the resulting record material will be white or bluish white in color, and a colored mark will appear thereon as the result of the application of localized pressure.

This pressure-sensitive record material is not substantially aifected by the amount of atmospheric humidity ordinarily encountered, although the mark may fade somewhat if subjected to high humidity for a long-continued period of time. However this pressure-sensitive record material does not become stained or discolored by exposure to high humidity for long periods of time, and retains its ability to respond to the application of localized pressure, and to produce the mark of distinctive color, under such conditions. This is thought to be due to the fact that the record material does not include any hygroscopic ionizing media. Consequently, the structure of the record material is not altered or modified due to the absorption of water from the atmosphere.

A method that has been used successfully to make the pressure-sensitive record material described above is as follows: A slurry of kaolin and water was prepared including fifty parts by Weight of kaolin to fifty parts by weight of water, and a small amount of a suitable dispersing agent, such as sodium metaphosphate, for instance, in the proportion of 0.075% by weight was added to facilitate the dispersion of the particles of kaolin throughout the slurry. The addition of this dispersing agent reduces the viscosity of the slurry considerably, thus facilitating its mixing and application, and also preventing the settling of the solid particles of kaolin. A 20% by weight solution of casein in water was formed by, first, dispersing the casein in cold water by stirring for fifteen minutes at room temperature and, then, heating up to 60 degrees centigrade. Five parts by weight of a 28% ammonium hydroxide solutionthat is, one having a specific gravity of 25.9 323., at

were then added to the hot casein solution, which was stirred for about fifteen minutes and allowed to cool to room temperature. The kaolin slurry and the alkaline casein solution were then thoroughly mixed and blended, in the ratio of ten parts by weight of kaolin to one part of casein, and, at this stage, a small percentage-for instance, about 0.05% by weight-of a solution of equal parts by weight Of tributyl phosphate in alcohol, or other anti-foaming agent, was added. This mixture of the kaolin slurry and the casein solution was then applied as a coating to the paper, and the coated paper was dried and calendered or treated in any desired way to give the proper surface finish. A solution in toluene of about 3% by weight of the selected phthalide material was then applied to the coated side of the paper, the excess of this solution was removed in any suitable way, as by passing under a doctor blade, and then the treated paper was dried to evaporate the toluene, and was ready for use.

The pressure-sensitive record materials disclosed herein are not claimed in this application but are disclosed and claimed in the pending application of Barrett K. Green, Serial No. 784,939, filed November 8, 1947, for Pressure-sensitive record material, and in a division, Serial No. 59,426, filed November 10, 1948.

It is understood that the process of making a pressure-sensitive record material described herein is susceptible of considerable variation without departing from the spirit of the invention.

What is claimed is:

1. The process of making a pressure-sensitive record material including the forming on a supporting member a film-like deposit of solid particles of a plurality of adsorption color-forming reactants disposed in contiguity with each other and a solid insulating medium, derived from an organic film-forming hydrophilic colloid material, insulating said reactant particles from color-forming reaction with each other, at least one of said reactants being an inorganic compound and at least another of said reactants being an organic compound adsorbable therewith, and said reactants being so selected as to react, in the absence of a liquid ionizing medium for the reactants, to form a distinctive color when brought into adsorption contact with each other, one of said color-forming reactants having the structure o [Elmo wherein R is selected from the group consisting of the ethyl radical C2H5 and the normal propyl radical C3H7 and the inorganic reactant being in fine particle form providing a large adsorbent surface area and which is an acid relative to the organic reactant so as to be an electron acceptor when in adsorption contact with said organic reactant.

2. The process of making a pressure-sensitive record material including the steps of coating a supporting member with a film of solid insulating material, derived from an organic film-forming hydrophilic colloid substance, having particles of a first color-forming solid reactant dispersed therein, and depositing on said film particles of a second color-forming solid reactant, one of said reactants being an inorganic compound and the other reactant being an organic compound adsorbable therewith, and said reactants being so selected as to form a distinctive color when brought into adsorption contact with each other, said solid insulating material being such as to insulate the reactants from colorforming reaction contact with each other, and said second color-forming reactant, having the structural formula 8 wherein TR is selected :from rthe :group :consisting of the ethyl radicakGzHaandithe normal propyl FEFERENCES CITED radical Cs-H'z and the inorganic reactant beingfin The rfollowmg r fe :ar 0 ar rdiinxthe "fine particle form providing a large adsorbent file i :organic reactant sowas toi be an-electron acceptor when I-in adsorption contact with said organic reactant.

surface area and-Which is anaciti'relative tolme :5 EFQREIGNPATENTS Number Country Date 550,332 fireatfBritain. J-an. .4, .1943

BARRETT 'IK. GREEN. 

1. THE PROCESS OF MAKING A PRESSURE-SENSITIVE RECORD MATERIAL INCLUDING THE FORMING ON A SUPPORTING MEMBER A FILM-LIKE DEPOSIT OF SOLID PATTICLES OF A PLURALITY OF ADSORPTION COLOR-FORMING REACTANTS DISPOSED IN CONTIGUITY WITH EACH OTHER AND A SOLID INSULATING MEDIUM, DERIVED FROM AN ORGANIC FILM-FORMING HYDROPHILIC COLLID MATERIAL, INSULATING AND RECTANT PARTICLES FROM COLOR-FORMING REACTION WITH EACH OTHER, AT LEAST ONE OF SAID REACTANTS BEING AN INORGANIC COMPOUND AND AT LEAST ANOTHER OF SAID REACTANTS BEING AN ORGANIC COMPOUND ADSORBABLE THEREWITH, AND SAID REACTANTS BEING SO SELECTED AS TO REACT, IN THE ABSENCE OF A LIQUID IONIZING MEDIUM FOR THE REACTANTS, TO FORM A DISTINCTIVE COLOR WHEN BROUGHT INTO ADSORPTION CONTACT WITH EACH OTHER, ONE OF SAID COLOR-FORMING REACTANTS HAVING THE STRUCTURE 